DESIGN & OPTIMIZATION OF 800 KV TRANSMISSION LINE Gopal Ji AGM (Engineering TL Dept.) Power Grid Corporation of India limited Gurgaon, India MAJOR COMPONENTS OF A TRANSMISSION LINE Conductor Towers (and Foundations) Earthwire Insulators ] Insulator Hardware Fittings ] strings Accessories BASIC DESIGN ASPECTS Electrical Design Aspects Power Flow / Line Loadability Electrical Clearances (Operational, safety) Corona & Interference Insulation Requirements Mechanical Design Aspects External (Dynamic) loads due to wind, ice etc. Self Weight of components Temperature conditions, Climatological factors Vibrations TRANSMISSION LINE OPTMIZATION Involves simultaneous/parallel studies for design & selection of various components of transmission line to achieve overall optimum techno-economic design TRANSMISSION LINE DESIGN OPTIMIZATION Bundle Conductor studies Tower Design Study Tower Config. Analysis Review of Existing systems & Practices Selection of clearances Insulator string design Line Cost & Optimization Tower Fdn. Study Economic Eval. Of Line Results DESIGN AND OPTIMISATION OF POWER TRANSMISSION LINES Review of existing system and practices Selection of clearances Insulator and insulator string design Insulator Hardware Bundle conductor studies Tower configuration analysis Tower weight estimation Foundation volumes estimation Line cost analysis & span optimization Economic evaluation of line REVIEW OF EXISTING SYSTEM AND PRACTICES Review of practice adopted in different countries as well as India w.r.t following - Clearances adopted for different insulation levels - Swing angles adopted and clearances thereof - Configuration & Rating of insulator string, no of discs per string - Bundle conductor configuration, diameter of conductor - Surface gradient, Electric field, AN,TVI, RIV limitations SELECTION OF CLEARANCES Tower Clearance (Strike Distance) for different swing angles Phase to Phase Spacing Ground Clearance Mid Span Clearance and Shielding Angle Right of Way Clearance SELECTION OF CLEARANCES Strike distance (Live metal clearances): Clearance requirements are to be based on two assumptions; - In still air or under moderate winds, the clearance should be sufficient to withstand the lightning or switching impulse voltages. - Under high wind, the clearance should be adequate to meet the power frequency voltage requirements. Required Clearances are ascertained thru’ Insulation Co-ordination Studies Phase to Phase Clearances: Dictated by live metal clearances for standard tower configurations adopted in India Ground Clearances: Min clearance Based on I.E rules and interference criteria (Electric field, surface gradient, AN, RIV) Mid Span Clearance: Between earthwire and conductor: Based on voltage level, span etc. Right of Way Clearance: Based on I.E. rules Insulator string Maximum sag of conductor ROW = 42.5 X 2 = 85M MIN. GROUND CLEARANCE=15M 55 deg swing 7m MAXM. SAG=14.5 M 16.0 M Phase to Phase Clearance 9.0 M elect. Clearance required as per IE Rules 21.5 sin 55 = 17.50 M 9.0M + 17.5M +16.0 =42.5M 765kV S/C TRANSMISSION LINE: RIGHT OF WAY CALCULATIONS INSULATION CO-ORDINATION Insulation co-ordination aims at selecting proper insulation level for various voltage stresses in a rational manner. The objective is to assure that insulation has enough strength to meet the stress on it. How many Flashovers? Strength Insulation Flashover Probability Over Voltage Probability Density Stress Voltage-kV INSULATION CO-ORDINATION The maximum over voltage occurs rarely and like wise insulation strength very rarely decreases to its lowest value. The likelihood of both events occurring simultaneously is very limited. Therefore considerable economy may be achieved by recognizing the probabilistic nature of both voltage stress and insulation strength and by accepting a certain risk of failure. This leads to substantial decrease in line insulation, spark distances, tower dimensions, weight, ROW resulting in decreased cost of line. The decrease in line cost must be weighed against the increased risk of failure and the cost of such failures. TYPICAL POWER FREQUENCY AC FLASHOVER CHARACTERISTICS OF LARGE AIR GAPS Critical Flashover Voltage (Crest),kV TYPICAL AIR GAP SWITCHING SURGE CFO's 3000 2500 2500 2000 1500 1000 500 0 1 2 3 4 5 6 Gap Spacing,m Rod to Plane Insulator string Conductor to Tower Leg Conductor to Conductor Vertical Rod to Rod Critical Flashover Voltage,kV 2000 1500 1000 500 0 3 4 6 8 10 12 Gap Spacing,m Rod to Plane Tower Window Horizontal Rod to Rod BUNDLE CONDUCTOR SELECTION AND OPTIMISATION Size, Type and Configuration of Conductor influences - Tower and its geometry - Foundations - Optimum spans - Rating and configuration of Insulator string - Insulator swings - Ground clearance - Line interferences like electric field at ground, corona, radio & TV interference, audible noise etc CONDUCTOR SELECTION SCENARIOS Scenario I Selection of conductor for a transmission line of identified voltage level and specified minimum power flow but power flow capacity becomes ruling factor in selection of conductor size (low voltage lines). Scenario II Selection of conductor for a transmission line with identified voltage level and a specified minimum power flow but voltage level becomes ruling factor in selection of conductor/conductor bundle size (EHV/UHV lines). Scenario III Selection of conductor for high power capacity long distance transmission lines where selection of voltage level and conductor/conductor bundle size are to be done together to obtain most optimum solution (HVDC Bipole). CONDUCTOR BUNDLE SELECTION: METHODOLOGY Preliminary set of conductor bundle/ sizes identified to start optimization Parameters like insulation requirements, limits for corona, RIV,TVI,AN,EF,thermal ratings, line losses and statutory clearances identified Detailed analysis of various alternatives in respect of following to be carried out to select the configuration - Basic insulation design and insulator selection - Tower configuration analysis - Tower weight and foundation cost analysis - Capital line cost analysis and span optimization - Line loss calculations - Economic evaluations (PWRR) of alternatives - Comparison of interference performance - Cost sensitivity analysis Conductor Current Carrying Capacity Conductor Heat Balance Heat Generated = Heat Dissipated Heat Generated = I2R + Solar radiation (qs) Heat Dissipated = Convection Cooling (qc)+ Radiation Cooling (qr) I2R = (qr) + (qs) - (qs) The above equation solved for conductor temperature at point of heat balance CURRENT CARRYING CAPACITY: VARIATION W.R.T AMBIENT TEMPERATURE Current Carrying Capacity (Amp) 1200 1000 800 600 400 200 0 20 25 30 35 40 45 50 Conductor- ACSR Moose Max Temp 75deg C Solar Radiation: 1045 W/sqm Wind Speed 2Km/hr Absorption Coeff: 0.8 Emmisitivity coeff: 0.45 Ambient Temp (degC) Conductor Current Carrying Capacity : Variation w.r.t Max. Permissible Temp 1400 Current Carrying Capacity (degC) 1200 1000 800 600 400 200 0 65 75 85 95 115 125 Conductor- ACSR Moose Ambient Temp: 45 degC Solar Radiation: 1045 W/sqm Wind Velocity :2km/hr Absorption Coeff: 0.8 Emmisitivity Coeff: 0.45 Max Permissible Temp (deg C) CONDUCTOR SURFACE GRADIENT Conductor Surface gradient depends upon voltage level, number & dia of conductors, bundle configuration, phase spacing, clearances etc. Average Surface gradient E AVG= Q/ (2r) Where Q = [C] [V] & r = conductor radius Maximum Surface gradient E MAX= E AVG (1+d(n-1)/D) Where d = sub conductor diameter D = conductor bundle diameter N = number of sub conductors r=Conductor radius CORONA OR VISIBLE DISCHARGE Corona discharges form at the surface of the transmission line conductor when the electric field intensity (surface gradient) on the conductor surface exceeds the breakdown strength of the air. Critical surface voltage gradient To determine the onset gradient E peak of a conductor , the following formulae is used E peak= 31m (1+.308/ r) m=Surface roughness factor (.9 for dry .6 for rain) = Relative air density, r=Conductor radius Corona onset gradient should be greater than max conductor surface gradient. E peak> E MAX INTERFERENCE Produced by Transmission Lines Electric field at ground Magnetic field (not a predominant issue for EHV/UHV lines) Audible Noise Radio Interference ELECTRIC FIELD 12 ELECTRIC FIELD (KV/M) 10 8 6 4 2 0 0 10 20 30 40 50 60 LATERAL DISTANCE FROM CENTER PHASE (M) 400kV D/C (Twin Moose) 800kV S/C (Quad Bersimis) 400kV S/C (Twin Moose) MAXIMUM EXPOSURE TIME FOR HUMAN BEINGS UNDER VARIOUS ELECTRIC FIELDS GRADIENT (KV/M) 5 10 15 20 25 TIME (MIN.) Unlimited 180 90 10 6 AUDIBLE NOISE STUDY RESULTS RI (db/1uV/M at 1MHz) RADIO INTERFERENCE STUDY RESULTS 56 54 52 50 48 46 44 42 40 38 36 34 32 30 28 26 24 22 0 10 20 30 40 50 60 70 Audible Noise L50 (dB above 20 micro pascal) 60 50 40 5 10 15 20 25 30 35 40 LATERAL DISTANCE FROM OUTER PHASE (M) 400KV S/C (Twin Moose) 400 KV D/C (Twin Moose) 800KVS/C (Quad Bersimis) LATERAL DISTANCE (M) 400 kV , Grd Clearance= 9m 800kV, Grd. Clearance= 31.5m 800kv, Grd. Clearance= 23.5m PSYCHOLOGICAL EFFECTS OF AUDIBLE NOISE 60 AUDIBLE NOISE (dB) HIGH NUMEROUS COMPLAINTS 58 56 54 52 50 48 LOW NO COMPLAINTS MODERATE SOME COMPLAINTS DESIGN OF TOWERS Transmission Line Towers are designed as per IS:802:1995 considering wind zones as per IS:875:1987 SALIENT DESIGN CONDITIONS RELIABILITY REQUIREMENTS SECURITY REQUIREMENTS CLIMATIC LOADS UNDER NORMAL CONDITION FAILURE CONTAINMENT LOADS UNDER BROKEN WIRE CONDITION LOADS DURING CONSTRUCTION AND MAINTENANCE LOAD. SAFETY REQUIREMENTS Reliability Levels RELIABILITY LEVEL 1 2 RETURN PERIOD 50 150 SUGGESTED FOR FOR EHV TRANS LINES UPTO 400KV CLASS FOR TRANS LINES ABOVE 400KV CLASS AND TRIPLE & QUAD CIRCUIT TRANS LINE UPTO 400KV. FOR TALL RIVER CROSSING TOWERS AND SPECIAL TOWERS. 3 500 TOWER LOADING Wind Effects:i). Basic wind speed Wind Zone: 1 2 3 4 5 6 Vb(m/sec): 33 39 44 47 50 55 ii). Reference wind speed (Vr=Vb/k0) k0=1.375 iii). Design wind speed Vd = Vr.K1.K2 Where K1 = risk coefficient factor k2 = terrain coefficient factor iv). Design Wind Pressure 0.6 Vd. Vd. Loads Due To Conductor & Earthwire i). Transverse Load a). Due to Conductor & Earthwire. Pd . Cdc. L . Gc. d b). Due to insulator string. Where, Cdi. Pd. Ai . Gi Pd = Design wind pressure c). Deviation loads Cdc, Cdi = Drag co-officients 2T. Sin(D/2) L = Wind span Gc, Gi = Gust response factors ii). Vertical Load iii). Longitudinal Load d = Dia of cable T = Design tension D = Deviation angle Analysis And Design ANALYSIS i). GRAPHICAL METHOD ii). ANALYTICAL METHOD iii). COMPUTER AIDED ANALYSIS (K) (A) = (P) DESIGN AS COMPRESSION AND TENSION MEMBERS. CODAL PROVOSION FOR LIMITING COMPRESSION MEMBER DESIGN i). LEG MEMBERS ii). BRACINGS iii). REDUNDANTS iv). TENSION MEMBERS SLENDERNESS RATIO FOR 120 200 250 400 FLOW CHART FOR TOWER DESIGN NAME, VOLTAGE, CLASS, WIND ZONE & BASIC DESIGN PARAMETERS ( FROM APPROVED FR OR SEF GROUP) GEOLOGICAL CONSTRAINTS DETAILS OF ROUTE & BILL OF QUANTITIES (FROM SITE) DESIGN PHILOSPHY (FROM IS / IEC/ STANDARDISATION COMMITTEE REPORTS) INPUTS REVIEW CONFOIGURATION & TYPE OF TOWERS REVIEW TOWER LOADINGS & CONDITIONS REVIEW STURUCTIRAL ANALYSIS -BY COMPUTER -BY MANUAL VERIFICATION REVIEW FINAL DESIGN (THEORITICAL) STRUCTURAL DRAWINGS PROTO MANUFACTURE/ FABRICATION MODIFY DESIGN FAILED PROTO TESTING (FULL SCALE) SUCCESSFUL DESIGN FINALISED DESIGN STAGES TESTING & FINALISATION Classification of foundations Foundations are classified based on soil type and subsoil water level and listed below Normal Dry Sandy dry Wet Partially submerged Fully submerged Black cotton soil Dry fissured rock (Under cut type) Wet fissured rock (Under cut type) Submerged fissured rock (Under cut type) Hard rock Unequal chimney foundations are also povided to minimize the benching and for water logged area as well Design of Foundations Following ultimate foundation loads acting at the tower base (along the tower slope) are considered Down thrust (Compression) Uplift (Tension) Transverse side thrust Longitudinal side thrust Design checks •Check for Bearing capacity •Check for uplift capacity •Check for overturning •Check for sliding FLOW CHART FOR FOUNDATION DESIGN START MAXIMUM/ CRITICAL TOWER LOADINGS FROM TOWER DESIGN/ PREVIOUS SIMILAR FDN DESIGN , TOWER DIMENSIONS & SLOPE FROM TOWER DESIGN REVIEW FOUNDATION LOADINGS TYPE OF FDN FROM BOQ (SITE INPUT), SOIL PROPERTIES FROM SPECN/ SOIL INV. REPORT & CONCRETE PROPERTIES FROM SPECN REVIEW INPUTS DESIGN PHILOSPHY (FROM IS/ CBIP / (STANDARDISATION COMMITTEE REPORTS) FOUNDATION DESIGN BY COMPUTER /MANUALLY REVIEW REVIEW YES LARGE VARIATION WRT PREVIOUS SIMILAR DESIGN/ NIT ESTIMATE ? YES FOUNDATION DRAWINGS REVIEW FINALISATION END DESIGN FINALISED CAP & PIN DISC INSULATOR & INSULATOR STRINGS INSULATOR AND INSULATOR STRING DESIGN Electrical design considerations Insulation design depends on - Pollution withstand Capability Min. nominal creepage dist. = Min nominal specific creepage dist X highest system voltage phase to phase of the system levels Pollution Level Equiv. Salt Deposit Density (mg/cm2) Minm nominal specific creepage dist (mm/Kv) Creepage Distance of insulator string required for different pollution Light Medium Heavy 0.03 to 0.06 0.10 to 0.20 0.20 to 0.60 16 20 25 Very Heavy >0.60 31 - Switching/ Lightning Over voltage INSULATOR AND INSULATOR STRING DESIGN Mechanical design considerations a) Everyday Loading Condition Everyday load 20 to 25% of insulator rated strength. b) Ultimate Loading Condition Ultimate load on insulator to not exceed 70% of its rating. This limit corresponds roughly to pseudo-elastic limit. c) In addition, capacity of tension insulator strings at least 10 % more than rated tensile strength of the line conductors. Earthwire Function To protect conductor against lightning flashovers To provide a path for fault current Maximum allowable fault current (I) through earthwire mainly depends on Area of earthwire (A) Maximum permissible temperature Time of short circuit (t) I varies proportional to A and inverse proportion to sqrt (t) HARDWARE FITTINGS For attachment of insulator string to tower D-Shackles,Ball clevis, Yoke plate, Chain link For attachment of insulator string to the conductor Suspension & tension assembly Fittings like D-Shackles, Socket clevis, chain link For protection of insulator string from power follow current Arcing Horn For making electric field uniform and to limit the electric field at the live end Corona Control Ring/ Grading Ring For fine adjustment of conductor sag Sag Adjustment Plate, Turn Buckle HARDWARE FITTINGS-Design Suspension Assembly Shaped to prevent hammering between clamp & conductor To minimize static & dynamic stress in conductor under various loading conditions Minimum level of corona/RIV performance For slipping of conductor under prescribed unbalanced conditions between adjacent conductor spans Tension Assembly To withstand loads of atleast 95% of conductor UTS To have conductivity more than that of conductor Sag Adjustment Plate/ Turn Buckle To adjust sag upto 150mm in steps of 6mm Corona Control Ring/ Grading Ring To cover atleast one live end insulator disc To cover hardware fittings susceptible for Corona/RIV ACCESSORIES FOR CONDUCTOR & EARTHWIRE For joining two lengths of conductor/earthwire Mid Span Compression joint for Conductor/ earthwire For repairing damaged conductor Repair Sleeve For damping out Aeolian vibrations Vibration Damper for conductor & earthwire For maintaining sub conductor spacing along the span Spacers For damping out Aeolian vibrations, sub span oscillation and to maintain sub conductor spacing Spacer Damper ACCESSORIES FOR CONDUCTOR & EARTHWIRE- Design Mid Span Compression joint for Conductor/ earthwire & Repair Sleeve To withstand at least loads equivalent to 95% of the conductor UTS To have conductivity better than equivalent length of conductor (99.5% Aluminium) WIND INDUCED VIBRATIONS AEOLIAN VIBRATIONS High frequency, low amplitude vibrations induced by low, steady & laminar wind WAKE INDUCED VIBRATIONS Low frequency, medium amplitude vibrations induced by high velocity steady winds on bundle conductors GALLOPING Very low frequency, high amplitude vibrations induced by high velocity steady winds on conductors with asymmetrical ice deposit FACTORS INFLUENCING VIBRATION PERFORMANCE TYPE , STRANDING & DIA OF CONDUCTOR, EARTHWIRE CONDUCTOR/EARTHWIRE TENSION SUB-CONDUCTOR SPACING IN BUNDLE CONDUCTORS BUNDLE CONFIGURATION VIBRATION CONTROL DEVICES VIBRATION DAMPERS Commonly used for vibration control of single conductor systems as well as bundle conductors alongwith spacers SPACER DAMPERS Used for vibration control of bundle conductors (instead of combination of vibration dampers & spacers) First 765 kV Single Circuit Transmission Lines Of POWERGRID SALIENT DESIGN CONSIDERATIONS & IMPORTANT PARAMETERS OF 800KV KISHENPUR-MOGA TRANSMISSION LINE ELECTRICAL DATA A). NOMINAL VOLTAGE B). MAXIMUM SYSTEM VOLTAGE C). LIGHTNING IMPULSE WITHSTAND VOLTAGE D). POWER FREQUENCY WITHSTAND VOLTAGE (WET) E). SWITCHING IMPULSE WITHSTAND VOLTAGE (WET) F). MINIMUM CORONA EXTINCTION VOLTAGE (DRY) G). RIV AT 1 MHZ FOR PHASE TO EARTH VOLTAGE OF 510 kVrms 765KV 800KV 2400kVp 830 kVrms 1550 kVp 510kVrms 1000uV CONDUCTOR BUNDLE SELECTION (800 KV Kishenpur-Moga) QUAD ACSR BERSIMIS STRANDING - 42/4.57 + 7/2.54, DIA - 33.05 MM, WEIGHT - 2.181 KG/M, UTS - 154KN SUB-CONDUCTOR SPACING - 457 MM TOWERS, FOUNDATIONS (800 KV Kishenpur-Moga) - SELF SUPPORTING TYPE OF TOWERS FAMILY SELECTED : 0 DEG, 5 DEG & 15 DEG SUS. 30 DEG & 60 DEG TENSION REINFORCED CONCRETE TYPE FOUNDATIONS TOWER ELECTRICAL CLEARANCE (800 KV Kishenpur-Moga) ELECTRICAL CLEARANCE OF 1.3M CORRESPONDING TO 50 HZ. POWER FREQUENCY - TO BE MAINTAINED UNDER 55 DEG. SWING ANGLE. ELECTRICAL CLEARANCE OF 4.4 M CORRESPONDING TO SWITCHING SURGE LEVELS OF 1.75 p.u. - TO BE MAINTAINED UNDER 25 DEG. SWING ANGLE. ELECTRICAL CLEARANCE OF 5.1 M TO TOP & 5.6 M TO SIDE (+0.5M ADDED FOR LIVE LINE MAINTENANCE) - TO BE MAINTAINED UNDER STATIONARY CONDITIONS. PHASE CLEARANCE : 15M MID SPAN CLEARANCE : 9M SHIELDING ANGLE : 20 DEG. GROUND CLEARANCE : 15 M {BASED ON ELECTRICAL FIELD LIMIT OF 10KV/M.(AS PER IRPA/WHO GUIDELINES} - - INSULATORS (800KV Kishenpur-Moga) FOR SUSPENSION TOWERS : 0 DEG : DOUBLE SUSPENSION 120KN FOR I STRING (2X40) (IVI) SINGLE SUSPENSION 210 KN FOR V STRING(2X35 ) 5 DEG : DOUBLE SUSPENSION 120 KN FOR I STRING (2X40) (IVI) DOUBLE SUSPENSION 160/210KN FOR V STRING (2X2X35) - - 15 DEG:DOUBLE SUSPENSION 210 KN (4X35) (VVV) FOR TENSION TOWERS : QUAD TENSION 210 KN RIGHT OF WAY & INTERFERENCE (Kishenpur-Moga) RIGHT OF WAY - 85M ELECTRICAL FIELD AT EDGE OF RIGHT OF WAY < 2KV/M RI AND AN AT EDGE OF RIGHT OF WAY: AN(dBA) (WETCONDUCTOR) 58.2 55.9 56.5 54.2 VOLTAGE(kV) ALTITUDE(M) RI (DB) (FAIRWEATHER) 800 765 800 765 1000 1000 500 500 50.3 48.0 48.7 46.4 RI AND AN LEVELS ARE WITHIN INTERNATIONAL ACCEPTABLE LIMITS. LOADING CRITERIA (800 KV Kishenpur-Moga) WIND ZONE - 4 (47M/SEC BASIC WIND SPEED). 150 YEAR RETURN PERIOD. AS PER REVISED IS-802. DESIGN WIND PRESSURE ON CONDUCTOR - 1825 Pa NARROW FRONT WIND LOADING EQUIVALENT TO WIND SPEED OF 250 KM/HR. APPLIED ON TOWER BODY. RULING SPAN - 400 M MAXM. WIND SPAN - 400 M WEIGHT SPANS MAXM - 600M FOR SUSPENSION & 750 M FOR TENSION TOWERS MINM - 200M FOR SUSPENSION & -200M FOR TENSION TOWERS. - 800KV S/C KISHENPUR-MOGA TRANSMISSION LINE DESCRIPTION Conductor Bundle ALTERNATIVES/PARAMETERS/ RESULTS (I) 8 nos. ACSR types with dia ranging from 30.56mm to 38.2mm. (2) 5 nos. ACAR types with dia ranging from 30.40mm to 35.80mm. (3) 5 nos. AAAC types with dia ranging from 31.50mm to 35.8mm. 300 m,350 m,400 m,450 m,500 m,550 m,600 m Spans Basic Design Considerations (A) Wind Zone (B) Reliability Level (C) Power Flow (D) System Voltage Results (A) Optimum Conductor Bundle (B) Span i. Ruling ii. Maximum Wind Span iii. Weight Spans iv. Maximum ratio wind to weight span. Line Parameters (A) Clearances i. Live Metal Clearance ii. Minimum Ground Clearance iii. Minimum Phase Clearance (B) Insulator String i. Suspension Towers 0 deg. (I-V-I) 5 deg.(I-V-I) 15 deg. (V-V-V) (C) Interference Performance i. Audible Noise ii. Radio Interference Wind Zone 4 as per IS:875(1987) 2 as per IS:802 (1995) 2500 MW 800kV QUAD ACSR BERSIMIS 400 m 400 m 200 to 600 m for suspension towers, -200 to 750 m for tension towers 1.4 5.10 m for switching surge,1.3m for power frequency 15.0m 15.0 m Double I Suspension with 2x 40 nos, 120 kN disc insulators and single suspension V string with 35 nos, 210kN disc insulators in each arm. Double I Suspension with 2x 40 nos, 120 kN disc insulators and double suspension V string with 2x35 nos, 160/210kN disc insulators in each arm. Double V Suspension with 2x35 nos, 210kN disc insulators in each arm 58dBA 50 dB/1µV/m at 834 kHz 765 kV S/C Kishenpur-Moga Transmission Line (Horizontal Configuration) New Generation 765 kV Single Circuit Transmission Lines Of POWERGRID Special Features Delta Configuration with I V I Insulator Strings Reduced Right of Way - 64 m (instead of 85 m for Horizontal Configuration Lines) ROW = 85 Mts ROW = 64 Mts 765 kV S/C Delta Configuration Transmission Line 765 KV SUBSTATION AT SEONI 765 kV S/C Line - ELECTRIC FIELD (kV/m) 12 10 Electric Field (kV/m) 8 HORIZONTAL CONFIGURATION 6 DELTA CONFIGURATION 4 2 0 0 5 10 15 20 25 30 35 40 45 50 Lateral distance (m) 765 kV S/C Line - RADIO INTERFERENCE (dB/1 micro volt/m) 60 Radio Interference (dB/1 micro volt/m) 50 40 HORIZONTAL CONFIGURATION 30 DELTA CONFIGURATION 20 10 0 0 5 10 15 20 25 30 35 40 45 50 Lateral Distance (m) 765 kV S/C LINE - AUDIBLE NOISE (L5) 61 60 Audible Noise (dB above 20) 59 58 57 56 55 54 53 52 0 5 10 15 20 25 30 35 40 45 50 Lateral distance (m) HORIZONTAL CONFIGURATION DELTA CONFIGURATION 765 kV S/C LINE - AUDIBLE NOISE (L50) 59 58 57 Audible noise (dB above 20) 56 55 54 53 52 51 50 49 48 0 5 10 15 20 25 30 35 40 45 50 Lateral Distance (m) HORIZONTAL CONFIGURATION DELTA CONFIGURATION 765 kV Double Circuit Transmission Line DESIGN & OPTIMIZATION STUDIES FOR 765 KV D/C TRANSMISSION LINE Electrical Line Parameters (Same as 765 kV S/C) Nominal Line Voltage: 765kV r.m.s Maximum Line Voltage: 800kV r.m.s Switching Impulse Withstand level: 1550 kV peak Air gap clearances : 5.6 m at 0 deg 4.4 m at swing corresponding to 2 yr return period 1.3 m at swing corresponding to 50 yr return period DESIGN & OPTIMIZATION STUDIES FOR 765 KV D/C TRANSMISSION LINE Conductor – Bundle Alternatives Quad ACSR Moose Quad ACSR Bersimis Quad ACSR Lapwing Hexa ACSR Zebra Hexa ACSR Cardinal Hexa ACSR Moose (4* 31.77 mm dia) (4* 35.05 mm dia) (4* 38.2 mm dia) (6* 28.62 mm dia) (6* 30.4 mm dia) (6* 31.77 mm dia) DESIGN & OPTIMIZATION STUDIES FOR 765 KV D/C TRANSMISSION LINE Conductor Surface Gradients & Corona Onset Gradients Alternatives Quad Moose Quad Bersimis Quad Lapwing Hexa Zebra Hexa Cardinal Hexa Moose Max. Surface Gradient (kV/cm) 21.2 19.6 17.9 17.6 16.8 16.2 Fair Weather Corona Onset Gradient (kV/cm) 20 19.8 19.7 20.1 20 20 Electric Fields Alternatives Quad Moose Quad Bersimis Quad Lapwing Maximum E.F. Within ROW in kV/m 9.0 9.0 9.3 E.F. at ROW edge in kV/m 1.6 1.4 1.5 Hexa Zebra Hexa Cardinal Hexa Moose 10.0 10.0 10.0 1.9 1.9 1.9 DESIGN & OPTIMIZATION STUDIES FOR 765 KV D/C TRANSMISSION LINE Radio Interference Alternatives Quad Moose Quad Bersimis Quad Lapwing Hexa Zebra Hexa Cardinal Hexa Moose RIV at ROW edge in dB/µV/m 53.8 49.6 45.7 38.9 37.0 35.8 Audible Noise Alternatives Quad Moose Quad Bersimis Quad Lapwing Hexa Zebra Hexa Cardinal Hexa Moose A.N. at L5 LEVEL at ROW edge in dBA 63.8 63.2 62.0 58.5 58.1 57.7 A.N. at L50 LEVEL at ROW edge in dBA 62.8 61.6 59.6 54.6 53.7 52.9 DESIGN & OPTIMIZATION STUDIES FOR 765 KV D/C TRANSMISSION LINE Insulator Strings Conductor Bundle “I” Suspension String insulator rating Tension String insulator rating HEXA Zebra HEXA Cardinal HEXA Moose 2 X 160 ; 2 X 35 nos. 2 X 160 ; 2 X 35 nos. 2 X 160 ; 2 X 35 nos. 4 X 210 ; 4 X 35 nos. 4 X 320 ; 4 X 33 nos. 4 X 320 ; 4 X 33 nos. Comparative Capital Cost of Line Conductor Bundle Estimated Capital Cost (in Rs Lakhs per km) Percentage Increase HEXA Zebra HEXA Cardinal HEXA Moose 240 264 278 Base 10.0 % 15.8% DESIGN & OPTIMIZATION STUDIES FOR 765 KV D/C TRANSMISSION LINE Line Losses Conductor Bundle Losses (kW/km) at 2500 MVA/ckt Peak Average HEXA Zebra HEXA Cardinal HEXA Moose 286 245 232 115 98 93 Comparative PWRR Conductor Bundle PWRR of capital cost of line (in Rs lakhs/ km) PWRR of losses lakhs/km) (in Rs Total PWRR (in Rs lakhs/km) HEXA Zebra HEXA Cardinal HEXA Moose 360 396 417 390 334 317 750 730 734 765 KV D/C TOWER CONFIGURATION THANK YOU